Spatially-fed high-power amplifier with shaped reflectors

ABSTRACT

A spatially-fed high-power amplifier comprises one or more shaped reflectors to reflect an initial wavefront, and an active array amplifier to amplify the reflected wavefront to generate a high-power planar wavefront. The shaped reflectors provide the reflected wavefront with substantially uniform amplitude when incident on the active array amplifier. The initial wavefront may be a substantially spherical wavefront, and the shaped reflectors may compensate for any amplitude taper of the initial wavefront to provide the reflected wavefront with substantially uniform amplitude components for incident on the active array amplifier. In some embodiments, the shaped reflectors may also contour the illumination to fit the shape of the active array amplifier to help minimize spillover.

TECHNICAL FIELD

Embodiments of the present invention pertain to high-power amplificationof microwave energy.

BACKGROUND

Solid state generation of high-power radio frequency (RF) energy,particularly at high-microwave and millimeter-wave frequencies, islimited by the power output of individual transistors. For example, atW-band frequencies, currently available high-power transistors onlygenerate 50 to 100 milliwatts primarily because the transistors must berelatively small in size in order to have a useful gain. Due to thissize limitation, the output power of thousands of transistors must becombined to generate high-power levels of greater than 100 watts, forexample. Conventional power-combining techniques using waveguide ormicrostrip power combiners have substantial loss at W-band frequenciesand are ineffective. This is because as the output of more transistorsis combined, the distance between the transistors increases and the linelengths of the power combiners increase accordingly. This increases theinsertion loss of the combiner and the phase match error between eachleg of the combiner.

Thus, there are general needs for improved high-power RF amplifiers,particularly millimeter-wave and W-band high-power amplifiers.

SUMMARY

A spatially-fed high-power amplifier comprises one or more shapedreflectors to reflect an initial wavefront, and an active arrayamplifier to amplify the reflected wavefront to generate a high-powerplanar wavefront. The shaped reflectors provide the reflected wavefrontwith substantially uniform amplitude when incident on the active arrayamplifier. In some embodiments, the shaped reflectors may also contourthe illumination to fit the shape of the active array amplifier to helpminimize spillover. The initial wavefront may be a substantiallyspherical wavefront, and the shaped reflectors may compensate for anyamplitude taper of the initial wavefront to provide the reflectedwavefront with substantially uniform amplitude components for incidenton the active array amplifier.

In some embodiments, the shaped reflectors comprise a section of amodified paraboloid surface, a section of a modified hyperboloidsurface, or a section of a modified ellipsoid surface. The surfaces ofthe shaped reflectors may be represented by polynomials havingcoefficients selected to provide the reflected wavefront incident on theactive array amplifier substantially uniform in amplitude and contouredto fit the shape of the active array amplifier. The coefficients of thepolynomials may be iteratively adjusted until a simulated wavefrontincident on the active array is substantially uniform in amplitude. Theresulting coefficients may be used to generate the shapes of thereflective surfaces.

In some embodiments, the reflective surfaces comprise three-dimensional(3D) plastic surfaces having RF reflective coating disposed thereon. The3D plastic surfaces may be formed by a stereolithography process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a spatially-fed high-power amplifier for generatinga planar output wave in accordance with some embodiments of the presentinvention;

FIG. 1B illustrates a spatially-fed high-power amplifier for generatinga planar output wave in accordance with some other embodiments of thepresent invention;

FIG. 2 illustrates an amplifier cell of an array amplifier in accordancewith some embodiments of the present invention;

FIG. 3 illustrates a spatially-fed high-power amplifier for generating aplanar output wave in accordance with some other embodiments of thepresent invention;

FIG. 4 illustrates a spatially-fed high-power amplifier for generating ahigh-power RF signal in accordance with some embodiments of the presentinvention;

FIG. 5 illustrates a spatially-fed high-power amplifier for generating ahigh-power RF signal in accordance with some other embodiments of thepresent invention;

FIG. 6 illustrates a spatially-fed high-power amplifier for generating ahigh-power RF signal in accordance with yet some other embodiments ofthe present invention;

FIG. 7 illustrates the shaping of wavefronts by reflective surfaces inaccordance with some embodiments of the present invention;

FIG. 8 illustrates a three-dimensional view of an example electric fieldillumination on an active array amplifier; and

FIG. 9 is a flow chart of a procedure for generating shaped reflectorsin accordance with some embodiments of the present invention.

DETAILED DESCRIPTION

The following description and the drawings illustrate specificembodiments of the invention sufficiently to enable those skilled in theart to practice them. Other embodiments may incorporate structural,logical, electrical, process, and other changes. Examples merely typifypossible variations. Individual components and functions are optionalunless explicitly required, and the sequence of operations may vary.Portions and features of some embodiments may be included in orsubstituted for those of others. Embodiments of the invention set forthin the claims encompass all available equivalents of those claims.Embodiments of the invention may be referred to, individually orcollectively, herein by the term “invention” merely for convenience andwithout intending to limit the scope of this application to any singleinvention or inventive concept if more than one is in fact disclosed.

The present invention provides high-power amplifiers using spatial powercombining techniques which essentially use the air or free space toilluminate an array of power amplifier elements. In this way, theinsertion loss of this combining technique is about constant withrespect to the number of transistors. In some embodiments, the presentinvention provides a spatially-fed high-power amplifier that may be partof a high-power microwave transmitter suitable for use in acommunication system. In other embodiments, the present inventionprovides a spatially-fed high-power amplifier that may be suitable foruse in a directed energy system, although the scope of the invention isnot limited in this respect.

FIG. 1A illustrates a spatially-fed high-power amplifier for generatinga planar output wave in accordance with some embodiments of the presentinvention. Spatially-fed high-power amplifier 100 comprises feed horn102 to generate initial wavefront 103 from a low-power radio-frequency(RF) input signal 101. Spatially-fed high-power amplifier 100 alsocomprises reflectors 104 and 106 having RF reflective surfaces toreflect initial wavefront 103 and generate reflected wavefront 107.Spatially-fed high-power amplifier 100 also comprises active arrayamplifier 108 to amplify reflected wavefront 107 to generate ahigh-power planar wavefront 109. Reflective surfaces of RF reflectors104 and 106 are selected so that reflected wavefront 107 issubstantially uniform in amplitude when incident on active arrayamplifier 108. This is described in more detail below. In someembodiments, reflected wavefront 107 may be substantially uniform inamplitude and substantially coherent in phase, although the scope of theinvention is not limited in this respect. In some embodiments, reflectedwavefront 107 may also be substantially contoured to fit the shape ofactive array amplifier 108, although the scope of the invention is notlimited in this respect.

The spatially-fed high-power amplifiers of embodiments of the presentinvention are suitable for use with almost any RF frequency includingmicrowave frequencies and millimeter-wave frequencies, and particularlyW-band millimeter-wave frequencies, although the scope of the inventionis not limited in this respect.

In some embodiments, high-power planar wavefront 109 may be a collimatedwavefront (i.e., in a column), while in other embodiments, high-powerplanar wavefront 109 may be a converging or diverging wavefront.

In some embodiments, active array amplifier 108 may comprise a pluralityof substantially identical amplifier cells 110. Each amplifier cell 110may have a receive antenna to receive reflected wavefront 107, a poweramplifier to amplify RF signals received through the receive antenna,and a transmit antenna to transmit the amplified RF signals provided bythe power amplifier. The amplified RF signals transmitted by theplurality of amplifier cells 110 may comprise output wavefront 109.Initial wavefront 103 may comprise a substantially spherical wavefrontwith tapered amplitude components (i.e., a tapered illumination). Insome embodiments, feed horn 102 may be a horn antenna and low-power RFinput signal 101 may be provided in a waveguide structure, although thescope of the invention is not limited in this respect.

In some embodiments, the reflective surfaces of RF reflectors 104 and106 may be selected to compensate for the amplitude taper of initialwavefront 103 and to provide reflected wavefront 107 with substantiallyuniform amplitude components and coherent phase components for incidenton active array amplifier 108. In some embodiments, RF reflectivesurfaces of RF reflectors 104 and 106 may be represented by polynomialsor other mathematical functions having coefficients selected to providea wavefront incident on the active array that is substantially uniformin amplitude and substantially coherent in phase. In some embodiments,the surfaces are fabricated in accordance with the polynomials. Theseprocesses are described in more detail below.

In some embodiments, RF reflectors 104 and 106 may comprise a section ofa modified paraboloid surface, a section of a modified hyperboloidsurface and/or a section of a modified ellipsoid surface. In someembodiments, reflector 104 comprises a section of a modified paraboloidsurface to generate wavefront 105, and reflector 106 comprises a sectionof a modified hyperboloid surface to generate wavefront 107. In someembodiments, reflector 104 may be a sub-reflector and reflector 106 maybe a main reflector. Although many embodiments of the present inventionare illustrated and described with two reflectors, the scope of theinvention is not limited in this respect. Some embodiments of thepresent invention may use as few as one RF reflector, while otherembodiments may use three or more RF reflectors.

In some embodiments, the RF reflective surfaces of RF reflectors 104 and106 may comprise a three-dimensional (3D) plastic layer with a thin RFreflective (e.g., metallic) coating disposed thereon. In theseembodiments, the 3D plastic layer may be formed by a stereolithographyprocess described in more detail below.

FIG. 2 illustrates an amplifier cell of an array amplifier in accordancewith some embodiments of the present invention. Amplifier cell 210 maybe suitable for use as one cell 110 (FIG. 1A) of array amplifier 108(FIG. 1A), although other configurations are also suitable. Amplifiercells 210 may have substantially uniform gain and phase characteristics.In some embodiments, amplifier cells 210 may be individual semiconductordie while in other embodiments, the plurality of amplifier cells 210 maycomprise a single semiconductor die.

In some embodiments, each amplifier cell may include receive antenna 202to receive an incident wavefront, power amplifier 204 to amplify RFsignals received through receive antenna 202, and transmit antenna 206to transmit the amplified RF signals provided by power amplifier 204. Insome embodiments, the amplified RF signals transmitted by the pluralityof amplifier cells may comprise a planar output collimated wavefront.

In some embodiments, such as those illustrated in FIG. 1A, active arrayamplifier 108 (FIG. 1A) may be an active reflect array amplifier havingboth receive antennas 202 and transmit antennas 206 on a same side of aplanar surface to generate the planar output wavefront 109 (FIG. 1A) ina reflected direction. In these embodiments, output planar wavefront 109(FIG. 1A) may be viewed as a reflected high-power wavefront resultingfrom incident wavefront 107 (FIG. 1A).

In other embodiments, such as those illustrated in FIG. 3 describedbelow, the active array amplifier may be an active lens array amplifierhaving receive antennas 202 on a first side of the active arrayamplifier to receive the reflected wavefront from the RF reflectivesurfaces, and having transmit antennas 206 on a second opposite side ofthe active array amplifier to generate a planar output wavefront in athrough direction.

In accordance with some embodiments, reflected wavefront 107 (FIG. 1A)may be a uniform plane-wave with a power density level that willsaturate most or all of cells 210 (FIG. 2) in the array for efficientutilization of the array amplifier.

In some other embodiments, referred to as anti-taper embodiments,amplifier cells 210 (FIG. 2) may have their gain set to offset thetapered amplitude components of initial wavefront 103 (FIG. 1A) so thatarray amplifier 108 (FIG. 1A) generates the substantially uniformamplitude components and/or uniform phase components of output wavefront109 (FIG. 1A). In these embodiments, reflectors 104 and 106 do notnecessarily have to have their surfaces modified as described herein,although the scope of the invention is not limited in this respect.

In these embodiments, each amplifier cell 110 (FIG. 1A) may have itsgain set individually to cumulatively offset the tapered amplitudecomponents of non-planar input wavefront 103 (FIG. 1A) to generate thesubstantially uniform amplitude components of planar output wavefront109 (FIG. 1A). In these embodiments, an automatic gain control (AGC)process may be implemented by array amplifier 108 (FIG. 1A) toindividually control the gain of each amplifier cell 110 (FIG. 1A) sothat each unit cell may operate in at or near saturation, efficientlyutilizing the output power capability of the array amplifier.

Although embodiments of the present invention are described as usingreflective surfaces, the scope of the invention is not limited in thisrespect. In other embodiments, instead of one or more of reflectivesurfaces, RF lenses may be used. In these embodiments, the RF lenses maybe similarly selected and generated to generate incident planar waves onan amplifier array. In some other embodiments, a combination of shapedRF reflective surfaces and shaped lenses may be used.

In some embodiments, the present invention provides an amplifier withone or more shaped RF lenses to change amplitude and/or phasecharacteristics of initial wavefront 103 (FIG. 1A) and generatesubstantially uniform amplitude wavefront 107 (FIG. 1A). In theseembodiments, the shaped lenses may compensate for an amplitude taper ofinitial wavefront 103 (FIG. 1A) to provide wavefront 107 (FIG. 1A) withsubstantially uniform amplitude components for incident on active arrayamplifier 108 (FIG. 1A). In these embodiments, the shaped lenses mayalso be represented by polynomials having coefficients selected toprovide a wavefront incident on the active array amplifier withsubstantially uniform amplitude components.

FIG. 1B illustrates a spatially-fed high-power amplifier for generatinga planar output wave in accordance with some other embodiments of thepresent invention. Spatially-fed power amplifier 101 (FIG. 1B) issimilar to spatially-fed power amplifier 100 (FIG. 1A), howeverspatially-fed power amplifier 101 (FIG. 1B) includes polarizer grid 112positioned between reflector 106 and active array amplifier 108.Polarizer grid 112 may pass wavefronts of one polarization and mayreflect wavefronts of another polarization. In some embodiments,wavefront 107 may, for example, be horizontally polarized. In theseembodiments, polarizer grid 112 may pass horizontally polarizedwavefront 107, array amplifier 108 may receive the horizontallypolarized waves and may transmit vertically polarized waves (i.e., mayrotate the polarization). Polarizer grid 112 may reflect the verticallypolarized waves as wavefront 109. These embodiments of the presentinvention allow active array amplifier 108 to receive incident wavefront107 at a substantially normal angle to it surface. In these embodiments,receive antennas 202 (FIG. 2) and transmit antennas 206 (FIG. 2) of eachcell 210 (FIG. 2) of active array amplifier 108 may have orthogonalpolarizations. The terms horizontal and vertical are used herein asexamples of orthogonal polarizations and may be interchanged.Embodiments of the present invention may also be suitable for use withother orthogonal polarizations.

FIG. 3 illustrates a spatially-fed high-power amplifier for generating aplanar output wave in accordance with some other embodiments of thepresent invention. Spatially-fed high-power amplifier 300 comprises feedhorn 302 to generate initial wavefront 303 from low-power RF inputsignal 301, reflectors 304 and 306 having RF reflective surfaces toreflect initial wavefront 303 and generate reflected wavefront 307, andactive lens array amplifier 308 to amplify reflected wavefront 307 togenerate high-power planar wavefront 309. Reflective surfaces of the RFreflectors 304 and 306 may selected so that reflected wavefront 307 issubstantially uniform in amplitude when incident on active arrayamplifier 308.

In some embodiments, active lens array amplifier 308 may have receiveantennas, such as receive antennas 202 (FIG. 2), on first side 310 ofactive array amplifier 308 to receive reflected wavefront 307 from RFreflective surface 306. In these embodiments, active lens arrayamplifier 308 may have transmit antennas, such as transmit antennas 206(FIG. 2), on second opposite side 312 of active array amplifier 308 togenerate planar output wavefront 309 in the through direction asillustrated.

The spatially-fed amplifiers illustrated in FIGS. 1 and 3 radiate theamplified energy (i.e., in the air), however in some situations, thehigh-power may need to be utilized in a fashion that is not radiated.For example, it may need to be contained in a waveguide of other type oftransmission medium. Examples of some other embodiments of the presentinvention that provide high-power energy in a waveguide medium areillustrated in FIGS. 4-6 described below.

FIG. 4 illustrates a spatially-fed high-power amplifier for generating ahigh-power RF signal in accordance with some embodiments of the presentinvention. Spatially-fed high-power amplifier 400 comprises feed horn402 to generate initial wavefront 403 from low-power RF input signal401, reflectors 404 and 406 having RF reflective surfaces to reflectinitial wavefront 403 and generate reflected wavefront 407, and activereflect array amplifier 408 to amplify reflected wavefront 407 togenerate high-power planar wavefront 409.

In these embodiments, spatially-fed high-power amplifier 400 alsocomprises reflectors 410 and 412 having RF reflective surfacespositioned to reflect high-power planar wavefront 409 and generatesubstantially spherical output wavefront 413. In some embodiments,wavefront 409 may be collimated. In these embodiments, spatially-fedhigh-power amplifier 400 also comprises output feed-horn 414 to receivesubstantially spherical output wavefront 413 and generate high-power RFoutput signal 415. In some embodiments, output feed-horn 414 may be ahorn antenna and high-power RF output signal 415 may be provided withinan output waveguide, although the scope of the invention is not limitedin this respect.

In some embodiments, reflector 410 may comprise a section of a modifiedparaboloid surface and reflector 412 may comprises a section of amodified hyperboloid surface, although the scope of the invention is notlimited in this respect. Reflective surfaces of the RF reflectors 404and 406 may be selected so that reflected wavefront 407 is substantiallyuniform in amplitude when incident on active reflect array amplifier408.

FIG. 5 illustrates a spatially-fed high-power amplifier for generating ahigh-power RF signal in accordance with some other embodiments of thepresent invention. Spatially-fed high-power amplifier 500 comprises feedhorn 502 to generate initial wavefront 503 from low-power RF inputsignal 501, reflectors 504 and 506 having RF reflective surfaces toreflect initial wavefront 503 and generate reflected wavefront 507, andactive lens array amplifier 508 to amplify reflected wavefront 507 togenerate high-power planar wavefront 509.

In these embodiments, spatially-fed high-power amplifier 500 alsocomprises reflectors 510 and 512 having RF reflective surfacespositioned to reflect high-power planar wavefront 509 and generatesubstantially spherical output wavefront 513. In some embodiments,wavefront 509 may be collimated. In these embodiments, spatially-fedhigh-power amplifier 500 also comprises output feed-horn 514 to receivesubstantially spherical output wavefront 513 and generate high-power RFoutput signal 515. In some embodiments, output feed-horn 514 may be ahorn antenna and high-power RF output signal 515 may be provided withinan output waveguide, although the scope of the invention is not limitedin this respect.

In some embodiments, reflector 510 may comprise a section of a modifiedparaboloid surface and reflector 512 may comprises a section of amodified hyperboloid surface, although the scope of the invention is notlimited in this respect. Reflective surfaces of the RF reflectors 504and 506 may be selected so that reflected wavefront 507 is substantiallyuniform in amplitude when incident on active lens array amplifier 508.

FIG. 6 illustrates a spatially-fed high-power amplifier for generating ahigh-power RF signal in accordance with yet some other embodiments ofthe present invention. Spatially-fed high-power amplifier 600 comprisesfeed horn 602 to generate initial wavefront 603 from low-power RF inputsignal 601, reflectors 604 and 606 having RF reflective surfaces toreflect initial wavefront 603 and generate reflected wavefront 607, andactive reflect array amplifier 608 to amplify reflected wavefront 607 togenerate reflected high-power planar wavefront 609. Reflective surfacesof the RF reflectors 604 and 606 may selected so that reflectedwavefront 607 is substantially uniform in amplitude when incident onactive reflect array amplifier 608. In these embodiments, arrayamplifier 608 may be positioned to generate the high-power planarwavefront 609 in a direction directly opposite to reflected wavefront607 for reflection by reflectors 606 and 604 and for incidence on feedhorn 602. In this way, reflectors 606 and 604 generate a high-powerspherical wavefront incident on feed horn 602. Feed horn 602 maygenerate high-power RF output signal 615 from the high-power sphericalwavefront incident on feed horn 602. In these embodiments, orthomodetransducer 614 may be coupled with feed horn 602 to separate low-powerRF input signal 601 from high-power RF output signal 615, although thescope of the invention is not limited in this respect. In theseembodiments, orthomode transducer allows the horn to radiate a wavefront(the low-power input wavefront) of a first polarization (e.g., vertical)while simultaneously receiving a wavefront (the high-power outputwavefront) of a second polarization (e.g., horizontal). Array amplifier608 may use receive and transmit antennas of corresponding orthogonalpolarizations to receive the low-power input wavefront and generate areflected high-power output wavefront.

FIG. 7 illustrates the shaping of wavefronts by reflective surfaces inaccordance with some embodiments of the present invention. One problemwith spatially-fed arrays is the amount of energy that is spilled overthe rim of the array. This problem is exacerbated when the rim of thearray is a complex shape. Because most feed horns generate a circular orelliptical shaped beam, a lot of energy is wasted feeding an arrayamplifier that is not circular or elliptical. In accordance with someembodiments of the present invention, the illumination of the inputwavefront may be tailored to the shape of the array amplifier. In FIG.7, spherical wavefront 703 generated by feed horn 702 may be convertedto substantially planar wavefront 707 with reflectors 704 and 706. Inthese embodiments, the amplitude components of the electric field ofwavefront 707 may be tailored to the shape of amplifier array 708. Inthis example, the power may be concentrated within array 708 (i.e., withcut-out corners) and reduced outside the array, particularly at thecorners, so as to reduce wasted energy.

FIG. 8 illustrates a three-dimensional view of an example electric fieldillumination on an active array amplifier. In this example, outline 802may represent a square amplifier array. As illustrated, the electricfield within the region of the amplifier array is significantly greaterthan the electric field outside the amplifier array. As can be seen, theefficiency of a spatially fed amplifier may be significantly increasedby concentrating the energy within the shape of the amplifier array. Inthese embodiments, shaped reflective surfaces may be selected to providethis result.

FIG. 9 is a flow chart of a procedure for generating shaped reflectorsin accordance with some embodiments of the present invention. Procedure900 may be used to generate one or more shaped RF reflectors, such asreflectors 104 and 106 (FIGS. 1A and 1B), reflectors 304 and 306 (FIG.3), reflectors 404, 406, 410 and 412 (FIG. 4), reflectors 504, 506, 510and 512 (FIG. 5), reflectors 604 and 606 (FIG. 6) and reflectors 704 and706 (FIG. 7).

In operation 902, a first surface, such as surface 104 (FIG. 1A) isrepresented by a first polynomial describing a section of the firstsurface. In operation 904, a second surface, such as surface 106 (FIG.1A) is represented by a second polynomial describing a section of thesecond surface. The surfaces may, for example, be a paraboloid,hyperboloid or ellipsoid, although other three-dimensional surfaces mayalso be suitable.

In operation 906, amplitude and phase components of an incidentwavefront reflected by the surfaces may be simulated based on thepolynomials representing the surfaces. In some embodiments, the incidentwavefront may be a spherical wavefront such as wavefront 103 (FIG. 1A).

In operation 908, the coefficients of the polynomials representing thesurfaces may be iteratively adjusted until the reflected wavefront, suchas wavefront 107 (FIG. 1A), is substantially uniform in amplitude and/orcoherent in phase. In some embodiments, the coefficients may be adjustedto maximize a figure of merit to achieve a flat power density across thesurface of the array antenna. In some embodiments, an optimizationalgorithm may be used.

In operation 910, reflective surfaces may be generated based on thepolynomials resulting from operation 908. In some embodiments, operation910 may comprise generating the reflective surfaces out of metal (i.e.,with a computer controlled milling machine), although the scope of theinvention is not limited in this respect.

In other embodiments, operation 910 comprises generating the reflectivesurfaces using a stereolithography process. In these embodiments, thestereolithography process may comprise generating three-dimensionalcomputer models of the surfaces based on the polynomials and using anultraviolet laser to selectively harden layers of a liquid polymer basedon the computer model. In these embodiments, a three-dimensional modelof the surface may be created in a CAD program. The computer softwaremay “cut” the model into thin layers (e.g., five to ten layers permillimeter of thickness). An ultraviolet laser may “paint” one of thelayers exposing the top surface of the liquid plastic (i.e., aphotopolymer) in a tank and hardening it. The photopolymer may besensitive to ultraviolet light so that wherever the laser touches it,the polymer hardens. The platform drops down into the tank a fraction ofa millimeter, and then the laser “paints” the next layer on top of theprevious layer. This process may be repeated layer by layer until thethree-dimensional surface section is formed. The surface may be removedfrom the tank and rinsed with solvent to remove any uncured plastic.Each surface may then be cured in an ultraviolet oven to harden theplastic. The plastic surface may then be coated with an RF reflectivecoating such as a metallic paint or an electrolyses metallic plating,although the scope of the invention is not limited in this respect.

Although embodiments of the present invention are described as using anactive array amplifier, the scope of the invention is not limited inthis respect. In some embodiments, a passive array antenna, such as aflat aperture parabolic (FLAPs) antenna, may be fed with shapedreflectors or shaped lenses as described herein.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b)requiring an abstract that will allow the reader to ascertain the natureand gist of the technical disclosure. It is submitted with theunderstanding that it will not be used to limit or interpret the scopeor meaning of the claims.

In the foregoing detailed description, various features may beoccasionally grouped together in a single embodiment for the purpose ofstreamlining the disclosure. This method of disclosure is not to beinterpreted as reflecting an intention that the claimed embodiments ofthe subject matter require more features than are expressly recited ineach claim. Rather, as the following claims reflect, invention may liein less than all features of a single disclosed embodiment. Thus thefollowing claims are hereby incorporated into the detailed description,with each claim standing on its own as a separate preferred embodiment.

1. A spatially-fed high-power amplifier comprising: one or more shapedreflectors having an associated one or more radio-frequency (RF)reflective surfaces to reflect an initial wavefront and generate areflected wavefront; and an active array amplifier to amplify thereflected wavefront to generate a high-power planar wavefront, the oneor more reflective surfaces to provide the reflected wavefront withsubstantially uniform amplitude when incident on the active arrayamplifier.
 2. The amplifier of claim 1 wherein the initial wavefrontcomprises a substantially spherical wavefront, and wherein thereflective surfaces are to compensate for an amplitude taper of theinitial wavefront to provide the reflected wavefront with substantiallyuniform amplitude components for incident on the active array amplifier.3. The amplifier of claim 2 wherein the RF reflectors comprise at leastone of a section of a modified paraboloid surface, a section of amodified hyperboloid surface, or a section of a modified ellipsoidsurface, and wherein the reflective surfaces are represented bypolynomials having coefficients selected to provide the reflectedwavefront incident on the active array amplifier substantially uniformin amplitude.
 4. The amplifier of claim 2 wherein the RF reflectorscomprises a first reflector and a second reflector, the first reflectorcomprising a section of a modified paraboloid surface, the secondreflector comprising a section of a modified hyperboloid surface.
 5. Theamplifier of claim 4 wherein the active array amplifier is an activereflect array amplifier having a plurality of orthogonally polarizedreceive and transmit antennas on a same side of a planar surface togenerate the high-power planar wavefront in a reflected direction. 6.The amplifier of claim 5 wherein the receive antennas receive signalshaving a first polarization and the transmit antennas transmit signalsof a second orthogonal polarization, wherein the amplifier furthercomprises a polarizer grid positioned between the second reflector andthe active array amplifier, the polarizer grid to pass signals of thefirst polarization and to reflect signals of the second polarization,and wherein the high-power planar wavefront comprises signals of thesecond polarization.
 7. The amplifier of claim 4 wherein the activearray amplifier is an active lens array amplifier having a plurality ofreceive antennas on a first side of the active array amplifier toreceive the reflected wavefront and having a plurality of transmitantennas on a second opposite side of the active array amplifier togenerate the planar output wavefront in a through direction.
 8. Theamplifier of claim 4 further comprising: third and fourth reflectorshaving RF reflective surfaces positioned to reflect the high-powerplanar wavefront and generate a substantially spherical outputwavefront; and an output feed-horn to receive the substantiallyspherical output wavefront and generate a high-power RF output signal.9. The amplifier of claim 8 wherein the fourth reflector comprises asection of a modified paraboloid surface and the fifth reflectorcomprises a section of a modified hyperboloid surface.
 10. The amplifierof claim 9 wherein the active array amplifier is an active reflect arrayamplifier having a plurality of orthogonally polarized receive antennasand transmit antennas on a same side of a planar surface to generate thehigh-power planar wavefront in a reflected direction.
 11. The amplifierof claim 9 wherein the active array amplifier is an active lens arrayamplifier having a plurality of receive antennas on a first side of theactive array amplifier to receive the reflected wavefront and having aplurality of transmit antennas on a second opposite side of the activearray amplifier to generate the planar output wavefront in a throughdirection.
 12. The amplifier of claim 4 further comprising: a feed hornto generate the initial wavefront having the substantially sphericalwavefront; and an orthomode transducer coupled with the feed horn,wherein the array amplifier is positioned to generate the high-powerplanar wavefront in a direction opposite the reflected wavefront forreflection by the second and first reflectors for incidence on the feedhorn, and wherein the orthomode transducer separates a low-power RFinput signal used to generate the initial wavefront from a high-power RFoutput signal generated from the reflected high-power wavefront.
 13. Theamplifier of claim 1 wherein the active array amplifier comprises aplurality of substantially identical amplifier cells, each amplifiercell having a receive antenna to receive the reflected wavefront, apower amplifier to amplify RF signals received through the receiveantenna, and a transmit antenna to transmit the amplified RF signalsprovided by the power amplifier, wherein the amplified RF signalstransmitted by the plurality of amplifier cells comprise a planar outputcollimated wavefront.
 14. The amplifier of claim 3 wherein thecoefficients of the polynomials are iteratively adjusted until asimulated wavefront incident on the active array is substantiallyuniform in amplitude based on a simulated receipt of the initialwavefront, wherein the resulting coefficients are used to generateshapes of the reflective surfaces.
 15. The amplifier of claim 3 whereinthe reflective surfaces comprise three-dimensional (3D) plastic surfaceshaving RF reflective coating disposed thereon.
 16. The amplifier ofclaim 15 wherein the 3D plastic surfaces are formed by astereolithography process, and wherein the stereolithography processgenerates three-dimensional computer models of the surfaces based on thepolynomials and uses an ultraviolet laser to selectively harden layersof a liquid polymer based on the computer model to generate each plasticsurface.
 17. A spatially-fed high-power amplifier comprising: alow-power radio-frequency (RF) source to generate a non-planar inputwavefront; and an active array amplifier to receive the input wavefrontand to generate a planar output wavefront having substantially uniformamplitude components, the active array amplifier array comprising aplurality of amplifier cells, each amplifier cell having its gain setindividually to cumulatively offset tapered amplitude components of thenon-planar input wavefront to generate the substantially uniformamplitude components of planar output wavefront.
 18. The amplifier ofclaim 17 further comprising one or more reflectors having an associatedone or more radio-frequency (RF) reflective surfaces to reflect aninitial wavefront and generate a reflected wavefront for receipt by theactive array amplifier, wherein the RF source comprises a horn antennato generate a substantially spherical input wavefront.
 19. The amplifierof claim 18 wherein the RF reflectors comprise a first reflector and asecond reflector, the first reflector comprising a section of aparaboloid surface, the second reflector comprising a section of ahyperboloid surface.
 20. The amplifier of claim 19 wherein the activearray amplifier is an active reflect array amplifier having a pluralityof orthogonally polarized receive and transmit antennas on a same sideof a planar surface to generate a high-power planar wavefront in areflected direction.
 21. The amplifier of claim 20 wherein the receiveantennas receive signals having a first polarization and the transmitantennas transmit signals of a second orthogonal polarization, whereinthe amplifier further comprises a polarizer grid positioned between thesecond reflector and the active array amplifier, the polarizer grid topass signals of the first polarization and to reflect signals of thesecond polarization, wherein the high-power planar wavefront comprisessignals of the second polarization.
 22. The amplifier of claim 19wherein the active array amplifier is an active lens array amplifierhaving a plurality of receive antennas on a first side of the activearray amplifier to receive the reflected wavefront and having aplurality of transmit antennas on a second opposite side of the activearray amplifier to generate the planar output wavefront in a throughdirection.
 23. The amplifier of claim 19 further comprising; third andfourth reflectors having RF reflective surfaces positioned to reflectthe high-power planar wavefront and generate a substantially sphericaloutput wavefront; and an output feed-horn to receive the substantiallyspherical output wavefront and generate a high-power RF output signal,wherein the fourth reflector comprises a section of a paraboloid surfaceand the fifth reflector comprises a section of a hyperboloid surface.24. A spatially-fed high-power amplifier comprising: one or more shapedradio-frequency (RF) lenses to change amplitude and phasecharacteristics reflect an initial wavefront and generate asubstantially uniform amplitude wavefront; and an active array amplifierto amplify the substantially uniform amplitude wavefront to generate ahigh-power planar wavefront.
 25. The amplifier of claim 24 wherein theinitial wavefront comprises a substantially spherical wavefront, andwherein the shaped lenses are to compensate for an amplitude taper ofthe initial wavefront to provide the substantially uniform amplitudewavefront with substantially uniform amplitude components for incidenton the active array amplifier, wherein the shaped lenses are representedby polynomials having coefficients selected to provide the substantiallyuniform amplitude wavefront incident on the active array amplifier withsubstantially uniform amplitude.
 26. The amplifier of claim 24 whereinthe lenses comprise first and second lenses, and wherein the amplifierfurther comprises: third and fourth shaped lenses positioned to receivethe high-power planar wavefront and generate a substantially sphericaloutput wavefront; and an output feed-horn to receive the substantiallyspherical output wavefront and generate a high-power RF output signal.27. A spatially-fed millimeter-wave amplifier comprising: a first shapedreflector comprising a section of a modified paraboloid surface; asecond shaped reflector comprising a section of a modified hyperboloidsurface, the reflectors to reflect a substantially spherical initialwavefront and generate a reflected wavefront; and an active arrayamplifier to amplify the reflected wavefront to generate a high-powerplanar wavefront, wherein the reflective surfaces are to compensate foran amplitude taper of the initial wavefront to provide the reflectedwavefront with substantially uniform amplitude components for incidenton the active array amplifier.
 28. The amplifier of claim 27 whereinreflective surfaces of the reflectors are represented by polynomialshaving coefficients selected to provide the reflected wavefront incidenton the active array amplifier substantially uniform in amplitude,wherein the coefficients of the polynomials are iteratively adjusteduntil a simulated wavefront incident on the active array issubstantially uniform in amplitude based on a simulated receipt of theinitial wavefront, wherein the resulting coefficients are used togenerate shapes of the reflective surfaces.
 29. The amplifier of claim28 wherein the reflective surfaces comprise three-dimensional (3D)plastic surfaces having RF reflective coating disposed thereon, andwherein the 3D plastic surfaces are formed by a stereolithographyprocess.
 30. The amplifier of claim 29 wherein the active arrayamplifier comprises a plurality of substantially identical amplifiercells, each amplifier cell having a receive antenna to receive thereflected wavefront, a power amplifier to amplify RF signals receivedthrough the receive antenna, and a transmit antenna to transmit theamplified RF signals provided by the power amplifier, and wherein theamplified RF signals transmitted by the plurality of amplifier cellscomprise a planar output collimated wavefront.
 31. A method ofgenerating a high-power radio-frequency signal comprising: reflect aninitial wavefront with one or more shaped reflectors to generate areflected wavefront; and amplifying the reflected wavefront with anactive array amplifier to generate a high-power planar wavefront, theshaped reflectors having reflective surfaces to compensate for anamplitude taper of the initial wavefront to provide the reflectedwavefront with substantially uniform amplitude components for incidenton the active array amplifier.
 32. The method of claim 31 whereinreflective surfaces of the reflectors are represented by polynomialshaving coefficients selected to provide the reflected wavefront incidenton the active array amplifier substantially uniform in amplitude,wherein the coefficients of the polynomials are iteratively adjusteduntil a simulated wavefront incident on the active array issubstantially uniform in amplitude based on a simulated receipt of theinitial wavefront, and wherein the resulting coefficients are used togenerate shapes of the reflective surfaces.
 33. The method of claim 31wherein the reflective surfaces comprise three-dimensional (3D) plasticsurfaces having RF reflective coating disposed thereon, and wherein the3D plastic surfaces are formed by a stereolithography process.